A Phase 1/2 interventional study of SA53-OS (phase 1) and SA53-OS (phase 2) in Solid Tumor, sponsored by Lamassu Bio Inc. Recruiting at 3 sites in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-09.
Sponsored by Lamassu Bio Inc · Phase 1/2, Interventional, and Treatment
The objective of this study is to assess the safety, efficacy, and pharmacokinetics of SA53-OS in adult participants with refractory solid tumors.
The study is comprised of 2 parts: Part 1 called dose escalation, and Part 2a called dose expansion. This study starts with Part 1 where participants who are diagnosed with advanced or metastatic solid tumor cancers receive different doses of SA53-OS (starting with the lowest dose) to find the maximum tolerated dose (MTD) of SA53-OS. Once the MTD of SA53-OS is known, the study continues to Part 2a where participants who are diagnosed with dedifferentiated liposarcoma (DD LPS) or other solid tumor cancers will receive SA53-OS at the MTD.
The study drug, SA53-OS, will be administered for 3 consecutive days every 3 weeks as an oral solution for up to 2 years.
This is a phase 1/2a, open-label, dose escalation study conducted in adult participants with p53 wild-type refractory solid tumors. The study will assess the safety, efficacy, and pharmacokinetics of SA53-OS a novel MDM2 inhibitor capable of selective activation of p53. This enables the p53 tumor suppressor protein to selectively facilitate tumor cell death and growth inhibition.
The study drug, SA53-OS, will be administered for 3 consecutive days every 3 weeks as an oral solution. Phase 1 will consist of a dose escalation study to establish a candidate recommended phase 2 dose (RP2D). Phase 2a will enroll 2 expansion cohorts to establish any preliminary efficacy of SA53-OS in participants with dedifferentiated liposarcoma (DD LPS) with MDM2 amplifications and other p53 wild-type solid tumors as a single agent.
Phase 1 dose escalation:
Escalating doses of SA53-OS will be provided to participants with p53 wild-type refractory solid tumors to determine the RP2D. The MTD is the highest dose of a drug or treatment that does not cause unacceptable side effects in the first cycle. The RP2D considers all available safety, pharmacokinetics, and efficacy data including, the frequency, severity, and manageability of toxicities occurring after Cycle 1.
Phase 1 of the study will start with dose escalation by 2-fold (i.e., 2x preceding dose level) in cohorts of a single participant until Grade 2 or greater toxicity is observed.
When a single Grade 2 or higher toxicity is observed, 3+3 multi-participant cohorts will be treated at the dose in which the Grade 2 or higher toxicity was observed by enrolling another 2 participants at this dose. The 3+3 multi-participant cohorts will follow the standard 3+3 paradigm based on occurrence of any DLT with 50% dose escalation until the MTD is identified.
Phase 2a dose expansion:
The purpose of Phase 2a of the study is to describe any preliminary evidence of efficacy from SA53-OS monotherapy in participants with DD LPS or other p53 wild-type or MDM2 amplified solid tumors. Phase 2a will also be used to confirm the safety and tolerability of the candidate RP2D of SA53-OS determined in Phase 1 of the study, to further describe the toxicity and pharmacokinetics profiles of SA53-OS, and to assess potential biomarkers of sensitivity resistance, and toxicity.
Participants will continue to receive study treatment until either: 1) disease progression; 2) occurrence of unacceptable treatment-related toxicity as per participant or Investigator discretion; 3) the maximum of 2 years of treatment has been reached; or 4) other reason(s) for study treatment discontinuation. In the case of complete response, treatment should be continued for at least 6 months if no other stopping criteria are met, and further treatment can be recommended at the investigator's discretion.
160 studies on the registry are indexed under Liposarcoma; 36 are open to participants now.
This study's planned enrollment of 55 is close to the median of 52 across 136 interventional studies indexed under Liposarcoma.
Browse Liposarcoma studies →This is the only study on the registry with Lamassu Bio Inc as lead sponsor.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Tumor characteristics of participants in Phase 1
Tumor characteristics of participants in Phase 2a
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Able to have children. For women this usually means from the first period until menopause, unless permanently unable to through surgery; for men, unless permanently sterile. Read who the line is about — participants, women, men, or their partners.
Criteria about it usually ask for contraception during the study and for a time after it.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Line of therapy
A line of therapy is one course of treatment, which may combine several drugs. First-line is the first course given; second-line follows when that stops working or is not tolerated.
“Two prior lines” means two courses that count separately under the study’s rules — not simply two drugs. Ask the study team if you are unsure how yours are counted.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Measurable disease
The amount of disease can be tracked with a defined measurement, so the study can see whether it shrinks or grows. It might be a tumour measured on a scan or, in some blood cancers such as myeloma, a marker measured in blood or urine.
The criteria or the study team say which measurement counts — having no tumour visible on a scan does not by itself rule you out.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
RECIST
The standard rules for measuring tumours on CT or MRI scans, to tell whether a cancer is shrinking, stable or growing during treatment.
“Measurable disease per RECIST 1.1” usually means at least one tumour 10 mm or more at its longest on a CT scan, or a lymph node 15 mm or more across its short axis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECOG performance status
A scale of how much an illness limits everyday activity. For people being assessed to join a study, scores run from 0 (fully active) to 4; lower is more active.
Studies most often ask for 0–1 or 0–2. Your doctor gives the score; the WHO scale uses the same steps. The full scale also has 5, which records death.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Reproductive potential
Able to have children. For women this usually means from the first period until menopause, unless permanently unable to through surgery; for men, unless permanently sterile. Read who the line is about — participants, women, men, or their partners.
Criteria about it usually ask for contraception during the study and for a time after it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Brain metastases
Cancer deposits in the brain from a cancer that started elsewhere in the body (CNS metastases include the spinal cord).
Studies differ: some leave out any brain metastases, some accept ones treated and stable for some weeks. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
QT and QTc
On an ECG, the QT interval is the time the heart’s lower chambers take to activate electrically and recover in each beat. QTc is that time adjusted for heart rate (QTcF by Fridericia’s formula, QTcB by Bazett’s). Some medicines lengthen it, and a long QTc can raise the risk of a dangerous heart rhythm.
The study may name a correction formula and a limit in milliseconds, often around 450–480.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Dose escalation phase
Drug: SA53-OS (phase 1)
Cohort A: DDLPS (MDM2 amplified and p53 wild-type) Cohort B: other p53 wild-type solid tumors
Drug: SA53-OS (phase 2)
Dose escalation phase in which participants receive SA53-OS on 3 consecutive days every 3 weeks for a maximum of 2 years. Single participant cohorts will be enrolled until a Grade 2 or greater toxicity is observed and then 3+3 multi-participant cohorts will be enrolled until the MTD is identified.
Dose expansion phase in which participants receive SA53-OS on 3 consecutive days every 3 weeks for a maximum of 2 years at the MTD identified in phase 1.
Phase 1: Incidence of DLT
Incidence of DLT in Cycle 1 (Day 1 to 21)
Time frame: 21 days
Phase 1 and 2: Adverse events
Frequency of adverse events
Time frame: Approximately 2 years
Phase 1: Peak plasma concentration
Determine the pharmacokinetic profile of SA53-OS (Cmax)
Time frame: Day 4
Phase 1: Area under the plasma concentration versus time curve between 0 and 24 hours
Determine the pharmacokinetic profile of SA53-OS (AUC0-24)
Time frame: Day 4
Phase 1: Half-life
Determine the pharmacokinetic profile of SA53-OS (T1/2)
Time frame: Day 4
Phase 2: Objective response rate (ORR)
Participants achieving ORR defined as complete response (CR) rate plus partial response (PR) rate. CR: Disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to \<10 mm. PR: At least a 30% decrease in the sum of diameters of target lesions, taking as reference the baseline sum diameters.
Time frame: Approximately 2 years
Phase 2: Progression free survival (PFS)
Participants not meeting the definition for progressive disease
Time frame: Approximately 2 years
Phase 2: Overall survival
To evaluate overall survival
Time frame: Approximately 2 years
Phase 2: Duration of response
Duration of response will be evaluated in responders
Time frame: Approximately 2 years
Phase 2: Complete response rate
Participants achieving CR defined as disappearance of all target lesions. Any pathological lymph nodes (whether target or non-target) must have reduction in short axis to \<10 mm.
Time frame: Approximately 2 years
Phase 2: Stable disease rate
Participants achieving stable disease defined as neither sufficient shrinkage to qualify for PR nor sufficient increase to qualify for progressive disease.
Time frame: Approximately 2 years
Phase 2: Disease control rate
Participants achieving CR + PR + stable disease
Time frame: Approximately 2 years
Started Jun 2025 (actual). Primary completion is estimated for Jul 2031, 72 months after the start.
Since we started tracking on Sep 25, 2026, the dates moved once, on Nov 9, 2026: start Mar 2025 → Jun 2025, primary completion Dec 2026 → Jul 2031 and completion Dec 2028 → Aug 2031.
Earlier changes are on the record history on ClinicalTrials.gov ↗
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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